// Copyright 2020 Parity Technologies (UK) Ltd.
// This file is part of Polkadot.

// Polkadot is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Polkadot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.

//! Shows a basic usage of the `Overseer`:
//!   * Spawning subsystems and subsystem child jobs
//!   * Establishing message passing

use futures::{channel::oneshot, pending, pin_mut, select, stream, FutureExt, StreamExt};
use futures_timer::Delay;
use std::time::Duration;

use polkadot_node_primitives::{BlockData, PoV};
use polkadot_node_subsystem_types::messages::{
	CandidateBackingMessage, CandidateValidationMessage,
};
use polkadot_overseer::{
	self as overseer,
	dummy::dummy_overseer_builder,
	gen::{FromOverseer, SpawnedSubsystem},
	AllMessages, HeadSupportsParachains, OverseerSignal, SubsystemError,
};
use polkadot_primitives::v1::Hash;

struct AlwaysSupportsParachains;
impl HeadSupportsParachains for AlwaysSupportsParachains {
	fn head_supports_parachains(&self, _head: &Hash) -> bool {
		true
	}
}

////////

struct Subsystem1;

impl Subsystem1 {
	async fn run<Ctx>(mut ctx: Ctx) -> ()
	where
		Ctx: overseer::SubsystemContext<
			Message = CandidateBackingMessage,
			AllMessages = AllMessages,
			Signal = OverseerSignal,
		>,
	{
		'louy: loop {
			match ctx.try_recv().await {
				Ok(Some(msg)) => {
					if let FromOverseer::Communication { msg } = msg {
						tracing::info!("msg {:?}", msg);
					}
					continue 'louy
				},
				Ok(None) => (),
				Err(_) => {
					tracing::info!("exiting");
					break 'louy
				},
			}

			Delay::new(Duration::from_secs(1)).await;
			let (tx, _) = oneshot::channel();

			let msg = CandidateValidationMessage::ValidateFromChainState(
				Default::default(),
				PoV { block_data: BlockData(Vec::new()) }.into(),
				Default::default(),
				tx,
			);
			ctx.send_message(<Ctx as overseer::SubsystemContext>::AllMessages::from(msg))
				.await;
		}
		()
	}
}

impl<Context> overseer::Subsystem<Context, SubsystemError> for Subsystem1
where
	Context: overseer::SubsystemContext<
		Message = CandidateBackingMessage,
		AllMessages = AllMessages,
		Signal = OverseerSignal,
	>,
{
	fn start(self, ctx: Context) -> SpawnedSubsystem<SubsystemError> {
		let future = Box::pin(async move {
			Self::run(ctx).await;
			Ok(())
		});

		SpawnedSubsystem { name: "subsystem-1", future }
	}
}

//////////////////

struct Subsystem2;

impl Subsystem2 {
	async fn run<Ctx>(mut ctx: Ctx)
	where
		Ctx: overseer::SubsystemContext<
			Message = CandidateValidationMessage,
			AllMessages = AllMessages,
			Signal = OverseerSignal,
		>,
	{
		ctx.spawn(
			"subsystem-2-job",
			Box::pin(async {
				loop {
					tracing::info!("Job tick");
					Delay::new(Duration::from_secs(1)).await;
				}
			}),
		)
		.unwrap();

		loop {
			match ctx.try_recv().await {
				Ok(Some(msg)) => {
					tracing::info!("Subsystem2 received message {:?}", msg);
					continue
				},
				Ok(None) => {
					pending!();
				},
				Err(_) => {
					tracing::info!("exiting");
					return
				},
			}
		}
	}
}

impl<Context> overseer::Subsystem<Context, SubsystemError> for Subsystem2
where
	Context: overseer::SubsystemContext<
		Message = CandidateValidationMessage,
		AllMessages = AllMessages,
		Signal = OverseerSignal,
	>,
{
	fn start(self, ctx: Context) -> SpawnedSubsystem<SubsystemError> {
		let future = Box::pin(async move {
			Self::run(ctx).await;
			Ok(())
		});

		SpawnedSubsystem { name: "subsystem-2", future }
	}
}

fn main() {
	femme::with_level(femme::LevelFilter::Trace);
	let spawner = sp_core::testing::TaskExecutor::new();
	futures::executor::block_on(async {
		let timer_stream = stream::repeat(()).then(|_| async {
			Delay::new(Duration::from_secs(1)).await;
		});

		let (overseer, _handle) = dummy_overseer_builder(spawner, AlwaysSupportsParachains, None)
			.unwrap()
			.replace_candidate_validation(|_| Subsystem2)
			.replace_candidate_backing(|orig| orig)
			.build()
			.unwrap();

		let overseer_fut = overseer.run().fuse();
		let timer_stream = timer_stream;

		pin_mut!(timer_stream);
		pin_mut!(overseer_fut);

		loop {
			select! {
				_ = overseer_fut => break,
				_ = timer_stream.next() => {
					tracing::info!("tick");
				}
				complete => break,
			}
		}
	});
}
